Conventionally, a medium separating mechanism has been known in which plural overlapped media are separately carried one at a time (see, for example, Patent Literature 1). In the medium separating mechanism described in Patent Literature 1, a pull-in roller and a feed roller for carrying a medium from an upstream side to a downstream side are disposed on a lower side of a carrying passage in a carrying direction of a medium in a separated state with a predetermined distance therebetween. A tension roller is oppositely disposed to the pull-in roller and the feed roller from an upper side. Further, a reverse rotation roller which is rotated in the same direction as the pull-in roller and the feed roller is disposed on an upper side of the carrying passage between the pull-in roller and the feed roller in the carrying direction. A fixed block having an opposing face which faces the reverse rotation roller is disposed on a lower side of the reverse rotation roller. A space through which one piece of medium is capable of passing but two pieces of medium is unable to pass is formed between the opposing face of the fixed block and the reverse rotation roller.
In the medium separating mechanism described in Patent Literature 1, when two pieces of medium carried in an overlapped state in the upper and lower direction are reached to a position between the reverse rotation roller and the opposing face, since a tip end of an upper side medium is abutted with the reverse rotation roller, a force pushing to the upstream side is applied to the upper side medium by the reverse rotation roller and thus its carrying to the downstream side is prevented. On the other hand, a lower side medium is carried to the downstream side by a carrying force of the pull-in roller. In this manner, in the medium separating mechanism described in Patent Literature 1, overlapped media are separated by utilizing the space which is formed between the opposing face of the fixed block and the reverse rotation roller and the rotating force of the reverse rotation roller.